How to gracefully stop a HTTP2 server built with nghttp2 asio

I am aware of how to use nghttp2 asio library to build HTTP2 server and client applications.

The documentation says that there are stop and join APIs for gracefully stopping an HTTP2 server.

Is there any working example of using stop and join? In particular, as soon as listen_and_serve is called, the thread goes to a busy loop. Is it recommended to call stop from a different thread? Unfortunately no clue or example code is given in the documentation.